As long as no two headers define the same guard macro, the code will compile as expected. And if two headers do define the same guard macro, the programmer can go in and change one of them. #pragma once has no such safety net -- if the compiler is wrong about the identity of a header file, either way, the program will fail to compile.

If you decide to put the include guard in the including file, you should define the macro there as well: #ifndef HEADER_H #include "header.h" #define HEADER_H #endif But, as other answers have already said, it's much better to put the guard in the header itself: header.h : #ifndef HEADER_H #define HEADER_H /* contents of header.h */ #endif

2015年1月7日 · This header file has an include guard. However, I'm kind of confused as to what #define HEADER_FILE is actually doing. Let's say I were to forget the include guard, it would have been perfectly legal for me to completely ignore adding '#define HEADER_FILE'. What exactly are we doing when we define HEADER_FILE? What are we defining?

2017年8月13日 · Guard, round, and sticky bits of 0, 1, 1 tell you that the “residue bits” (by which I mean the bits starting just below the point where we are going to round) are .01xxx…, where xxx… is not known but contains at least one 1 bit. Thus, the “residue” portion is more than ¼ ULP (is .01 plus something positive) but less than ½ ULP (is ...

2016年4月11日 · Regardless, caching does come into play. How does the preprocessor know to include code outside of the guards. Example... extern int foo; #ifndef INC_GUARD #define INC_GUARD class ClassInHeader{}; #endif In this case the preprocessor will have to include extern int foo; multiple times if you include the same file multiple times.

2019年10月4日 · 1) A web guard is the traditional cookie store - so that web guard instructs Laravel to store and retrieve session information. 2) The API guard, on the other hand, uses tokens. So you would use the API guard if you want to authenticate users and requests using an API token in the header (bearer) or query parameter.

A web guard is the traditional cookie store - so that web guard instructs Laravel to store and retrieve session information the classic way. The API guard, on the other hand, uses tokens. So you would use the API guard if you want to authenticate users and requests using an API token in the header (bearer) or query parameter.

2014年5月16日 · #pragma once has several advantages compared to the macro-guard scheme, including less code, avoidance of name clashes, and sometimes improved compile speed. Doing some research, I realized that although #pragma once directive is supported by almost all known compilers, there's a turbidness on whether #pragma once directive is part of the C++11 ...

2011年1月22日 · The #ifndef/#define directives should be the first two lines of the file, and #endif should be the last. Include guards are only used in headers. Do not define your main function in a header: put it in an implementation file. If you have a header that will define a type and declare a function, but also needs a header itself:

2020年2月7日 · To use authentication for a custom guard in your package using Laravel 6, you will need to define your custom guard in the config/auth.php file. Here are the steps you can follow: Define your custom guard in the guards array of the config/auth.php file: